This invention relates to a system for coupling a towable ground-working implement to a towing vehicle, and in particular to such a system which transfers the weight of the implement, when it is in a raised transport position, to the entire towing vehicle, rather than to the rear end only, to minimize vertical lift at the rear of the vehicle.
There are many types of ground-working implements that are attachable to a tractor by means of a conventional three-point connection. Such a connection includes a pair of laterally spaced, lower support arms and a central, upper, longitudinally extensible arm by which the implement may be lifted upward out of contact with the ground for transport. Tractors provided with this type of three-point connection characteristically have sufficient forward weight to support the implement in transport condition without the latter causing sufficient lightening of the forward end to result in loss of steering traction.
On the other hand, other types of tractors are not provided with the above described three-point connection, but rather merely with a draw bar pivot connection. Accordingly, it has been the practice heretofore to provide a coupling between such a tractor connection and a three-point connection on a ground-working implement, by means of an interposed assembly of a wheeled frame provided with a rearwardly facing three-point connection for the implement and a forwardly extending tongue for connection to the tractor draw bar.
However, elevation of the implement at the three-point connection results in the wheeled frame functioning as a lever, developing an upward force at the forward end of the tongue and hence at the rear end of the tractor, sufficient to cause loss of driving traction.